The antiretroviral medication Truvada was recently approved by the FDA as a pre-exposure prophylaxis (PrEP) to reduce the risk of HIV infection among high risk uninfected individuals. A primary concern of PrEP as a prevention strategy is risk compensation, where PrEP users increase their risky sexual behaviors believing they can no longer be infected. Although the results from the PrEP efficacy trials did not find changes in risk behavior, it remains unclear how, and in what ways, rates of risky sex will change now that that Truvada is FDA approved. We propose to 1) examine sexual risk compensation over 12 months among men who have sex with men (MSM) who are initiating PrEP in a funded implementation study focused on PrEP adherence, and 2) enroll a control group of non-PrEP high risk MSM to compare sexual risk behaviors with the PrEP group over 6-months. By leveraging a currently funded PrEP demonstration cohort and adding a non-PrEP control group for comparison, this study will provide valuable information regarding risk compensation in a timely and cost-effective manner. Results will give physicians and health care administrators evidence to guide policies concerning PrEP usage, appropriate behavioral counseling strategies, and support for patient engagement and education for their health care.